For archiving facilities, warehouses, or companies having large amounts of articles to store, storage optimization is of utmost importance. Trying to reduce the amount of unused potential storage space in these facilities is a common concern.
Rudimentary storage racks having three, four, or more shelves or levels are used as storage means in some warehouses or the like facilities. These racks can support a certain number of palletized articles. Forklift vehicles are used to install palletized articles on the shelves of the racks.
Development directed towards storage optimization has led to more sophisticated storage systems. In particular, a known optimized storing system is the so-called push-back storage system. These push-back storage systems have a series of elongated storing lanes, the frontmost end of each lane defining a forklift access opening. Each lane comprises a number of frontwardly inclined pairs of rails and a number of carts each engaging a corresponding pair of rails. The pairs of rails are arranged in the following manner: the first or innermost pair of rails is the narrowest, and also vertically projects above the level of the other pairs of rails. The second and following pairs of rails are gradually wider and vertically lower than each preceding pair of rails. Each pair of rails is engaged by a corresponding cart which may roll therealong between a frontmost position near the forklift access opening, and a rearmost position away from the forklift access opening. The first cart engaging the innermost pair of rails is the narrowest, and the other carts are gradually wider than the preceding cart. A front stop member prevents the carts from rolling along the frontwardly downwardly inclined rails beyond the forklift access opening.
To store a first article-loaded pallet on such a storage system, the forklift places through the forklift access opening the article-loaded pallet over the vertically topmost and narrower cart. The first pallet is prevented from rolling beyond the forklift access opening under its own weight, by the abutment of its cart against the front stop member. Then, after having picked-up a second item-loaded pallet, the forklift horizontally pushes this second pallet against the first pallet, the latter being pushed back, with its cart rearwardly rolling along its corresponding first pair of rails against the rearwardly upward inclination of the rails, until the second topmost cart is cleared to allow the second pallet to be placed thereon. The second pallet, located near the forklift access opening, now abuts against the front stop member under its own weight and due to the frontwardly inclined rails, and the first pallet abuts against the second pallet.
This process can then be repeated until all carts are full: each new pallet comes to rest on the topmost available cart, after the preceding pallet-loaded carts have been pushed back up along the inclined rails.
To unload the pallets from the storage system, the pallets are recuperated by the forklift truck in a last-in first-out order. Thus, the frontmost article-loaded pallet is first retrieved, and by doing so, all the other stacked pallets are allowed to advance towards the forklift access opening, allowing a new frontmost pallet to be available at the storing lane forklift access opening. This advancement of the pallets towards the front end of the storage rack lane occurs automatically under their own weight by the rolling engagement of their respective carts on the inclined rails.
In push-back storage systems such as the one described hereinabove, the carts can support very heavy loads, and their movement about the rail assembly will often be significantly hampered by friction. Prior art storage systems comprise lanes that are longitudinally inclined at a 2° or 3° angle or more, to defeat the action of friction-borne forces resulting from the rolling engagement of the carts on the rails, and to allow the carts to readily roll towards the forklift access opening of the lane under the action of gravity-borne forces. These prior art rail inclination angles do not allow the use of storage systems having longer rails allowing a greater number of pallets to be loaded thereon, since the weight of the palletized articles will become too important to allow the forklift truck to push a greater number of pallets back when an additional article-loaded pallet is to be stored.
Also, prior art rails present flat top surfaces that do not prevent accumulation of macroparticulate debris thereover. This debris may eventually hinder or prevent the rolling engagement of the carts on the rails.